流和文件：保存和读取字节级数据

保存和读取字节级数据：

//写100000个随机数到一个文件中，非缓冲技术，同进测试操作时间
2

import java.io.*;
3

public class WriteUnbufferedTest
4

{
5

public static void main(String[] args)
6

{
7

try{
8

long start=System.currentTimeMillis(); //当前时间
9

FileOutputStream fsout=new FileOutputStream("sample.dat");
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System.out.println("start="+start);
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DataOutputStream out=new DataOutputStream(fsout);
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for(int i=0; i<100000; i++)
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out.writeDouble(Math.random());
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out.close();
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long stop=System.currentTimeMillis();
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System.out.println("stop="+stop);
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System.out.println("Time passed: "+(stop-start));
18

}catch(IOException ioe){
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System.out.println(ioe);
20

}
21

}
22

}
23

//写100000个随机数到一个文件中，缓冲技术，同进测试操作时间
2

import java.io.*;
3

public class WriteBufferedTest
4

{
5

public static void main(String[] args)
6

{
7

try{
8

long start=System.currentTimeMillis(); //当前时间
9

System.out.println("start="+start);
10

FileOutputStream fsout=new FileOutputStream("sample.dat");
11

BufferedOutputStream bfsout=new BufferedOutputStream(fsout);
12

DataOutputStream out=new DataOutputStream(bfsout);
13

for(int i=0; i<100000; i++)
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out.writeDouble(Math.random());
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out.close();
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long stop=System.currentTimeMillis();
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System.out.println("stop="+stop);
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System.out.println("Time passed: "+(stop-start));
19

}catch(IOException ioe){
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System.out.println(ioe);
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}
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}
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}
24

//非缓冲技术，读文件
2

import java.io.*;
3

public class ReadUnbufferedTest
4

{
5

public static void main(String[] args)
6

{
7

double sum=0;
8

try{
9

long start=System.currentTimeMillis();
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System.out.println("start="+start);
11

FileInputStream fsin=new FileInputStream("sample.dat");
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DataInputStream in=new DataInputStream(fsin);
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for(int i=0; i<100000; i++)
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sum+=in.readDouble();
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in.close();
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long stop=System.currentTimeMillis();
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System.out.println("stop="+stop);
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System.out.println("Average: "+(sum/100000));
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System.out.println("Time passed: "+(stop-start));
20

}catch(IOException ioe){
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System.out.println(ioe);
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}
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}
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}
25

//缓冲技术，读文件
2

import java.io.*;
3

public class ReadBufferedTest
4

{
5

public static void main(String[] args)
6

{
7

double sum=0;
8

try{
9

long start=System.currentTimeMillis();
10

System.out.println("start="+start);
11

FileInputStream fsin=new FileInputStream("sample.dat");
12

BufferedInputStream bfsin=new BufferedInputStream(fsin);
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DataInputStream in=new DataInputStream(bfsin);
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for(int i=0; i<100000; i++)
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sum+=in.readDouble();
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in.close();
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long stop=System.currentTimeMillis();
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System.out.println("stop="+stop);
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System.out.println("Average: "+(sum/100000));
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System.out.println("Time passed: "+(stop-start));
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}catch(IOException ioe){
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System.out.println(ioe);
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}
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}
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}
26

//创建简单程序，存储数据到sample.dat文件中
2

import java.io.*;
3

public class SimpleOutputTest
4

{
5

public static void main(String[] args)
6

{
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double pi=3.1415;
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int i=10;
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boolean okay=true;
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char ch='J';
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String s="Java C Pascal";
12

try{
13

FileOutputStream fsout=new FileOutputStream("sample.dat");
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DataOutputStream out=new DataOutputStream(fsout);
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out.writeDouble(pi);
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out.writeInt(i);
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out.writeBoolean(okay);
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out.writeChar(ch);
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out.writeUTF(s);
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out.close();
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}catch(FileNotFoundException fe){
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System.err.println(fe);
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}catch(IOException ioe){
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System.out.println(ioe);
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}
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}
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}
28

//创建简单程序读取数据
2

import java.io.*;
3

public class SimpleInputTest
4

{
5

public static void main(String[] args)
6

{
7

try{
8

FileInputStream fsin=new FileInputStream("sample.dat");
9

DataInputStream in=new DataInputStream(fsin);
10

double pi=in.readDouble();
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int i=in.readInt();
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boolean okay=in.readBoolean();
13

char ch=in.readChar();
14

String s=in.readUTF();
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in.close();
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System.out.println("pi="+pi+", i="+i);
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System.out.println("okay="+okay+", ch="+ch);
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System.out.println("s="+s);
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}catch(FileNotFoundException fnfe){
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System.err.println(fnfe);
21

}catch(IOException ioe){
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System.err.println(ioe);
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}
24

}
25

}
26

//创建SafeCopy程序来复制文件
2

//这个程序可以在命令中接收源文件名和目标文件名
3

//只当目标文件不存在时，程序才将源文件复制到现在要创建的目标文件中去
4

//即不覆盖原来已存在的文件
5

import java.io.*;
6

public class SafeCopy
7

{
8

public static void copyFile(DataInputStream in, DataOutputStream out) throws IOException
9

{
10

try{
11

while(true)
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out.writeByte(in.readByte());
13

}catch(EOFException eof){
14

return;
15

}
16

}
17

public static void main(String[] args)
18

{
19

String inFileName="E:\\101.asm", outFileName="E:\\500.txt";
21

File inFile=new File(inFileName);
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File outFile=new File(outFileName);
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if(!inFile.exists())
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System.out.println(inFileName+"does not exist.");
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else if(outFile.exists())
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System.out.println(outFileName+"already exist.");
27

else{
28

try{
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FileInputStream fsin=new FileInputStream(inFileName);
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BufferedInputStream bfsin=new BufferedInputStream(fsin);
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DataInputStream in=new DataInputStream(bfsin);
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FileOutputStream fsout=new FileOutputStream(outFileName);
33

BufferedOutputStream bfsout=new BufferedOutputStream(fsout);
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DataOutputStream out=new DataOutputStream(bfsout);
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copyFile(in,out);
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in.close();
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out.close();
38

}catch(IOException ioe){
39

System.out.println(ioe);
40

}
41

}
42

}
43

}
44

//用户首先输入需要复制文件的名称和路径，然后再输入新的文件名和路径，完成后将旧文件和新文件内容显示在屏幕上
2

import java.io.*;
3

public class txcopy
4

{
5

public static void main(String[] args)
6

{
7

byte[] b1=new byte[255];
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byte[] b2=new byte[255];
9

byte[] b3=new byte[2056];
10

byte[] b4=new byte[2056];
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int a=0;
12

int b=0;
13

try{
14

System.out.println("请输入源文件名称: \n");
15

a=System.in.read(b1,0,255);
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System.out.println("\n请输入目的文件名称: \n");
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b=System.in.read(b2,0,255);
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String sourceName=new String(b1,0,0,a-2);//把一个字节型数组转换成字符串数组
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String desName=new String(b2,0,0,b-2);
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System.out.println(sourceName.length());
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FileInputStream fileInput=new FileInputStream(sourceName);
22

int bytes1=fileInput.read(b3,0,2056);
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String sourceFile=new String(b3,0,0,bytes1);
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FileOutputStream FileOutput=new FileOutputStream(desName);
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FileOutput.write(b3,0,bytes1);
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fileInput=new FileInputStream(desName);
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int bytes2=fileInput.read(b4,0,2056);
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String desFile=new String(b4,0,0,bytes2);
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System.out.println("\n源文件内容为: \n");
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System.out.println(sourceFile);
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System.out.println("\n目的文件内容: \n");
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System.out.println(desFile);
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}catch(Exception e){
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System.out.println(e.toString());
35

}
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}
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}
38

//写一个程序显示在程序的命令中指定的目录中所有的文件和目录
2

//包括文件大小及是文件还是目录类型
3

//按字母顺序排序显示，并且目录在文件之前显示
4

import java.io.*;
5

import java.util.*;
6

import java.io.File;
7

class FileNameSorter implements Comparator
8

{
9

public int compare(Object o1, Object o2)
10

{
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File f1=(File)o1;
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File f2=(File)o2;
13

if(f1.isDirectory())
14

{
15

if(f2.isDirectory())
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return f1.getName().compareTo(f2.getName());
17

else
18

return -1;
19

}
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else
21

{
22

if(f2.isDirectory())
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return 1;
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else
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return f1.getName().compareTo(f2.getName());
26

}
27

}
28

public boolean equals(Object o1, Object o2)
29

{
30

return ((File)o1).getName().equals(((File)o2).getName());
31

}
32

}
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public class Dir
34

{
35

private static void showDirInfo(File list[])
36

{
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Arrays.sort(list, new FileNameSorter());
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for(int i=0; i<list.length; i++)
39

{
40

if(list[i].isDirectory())
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System.out.print("DIRECTORY");
42

else
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System.out.print(list[i].length()+"bytes");
44

System.out.println("\t"+list[i]);
45

}
46

}
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public static void main(String[] args)
48

{
49

// File path=new File(System.getProperty("user.dir"));//用户没有提供目录，则使用当前目录
50

File path=new File("D:\\j2sdk1.4.2");
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if(args.length>0)
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path=new File(args[0]);
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if(path.exists()&&path.isDirectory())
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showDirInfo(path.listFiles());
55

else
56

System.out.println("path not found or not directory");
57

}
58

}
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posted on 2005-11-16 16:46 newzpflying 阅读(1416) 评论(0) 收藏举报